U.S. patent number 6,251,323 [Application Number 09/367,046] was granted by the patent office on 2001-06-26 for plastic molding process and products produced thereby.
This patent grant is currently assigned to Royal Eco Products Limited. Invention is credited to Dave Cockle, Herbert K. Hoedl, Eufredo Maury.
United States Patent |
6,251,323 |
Hoedl , et al. |
June 26, 2001 |
Plastic molding process and products produced thereby
Abstract
The invention utilizes the adhesive properties which plastic
material exhibits while still hot combined with a multi stage
molding operation wherein one side of an insert or core located in
one side of a mold is coated with molten plastic on a first closing
of the mold, the mold is then opened with the plastic still hot to
remove the insert or core from the one mold side by virtue of its
adherence by the hot plastic to the other mold side, a second
charge of plastic is then introduced into the said one mold side
and the mold is closed again with the plastic in a molten state to
complete the encapsulation of the insert or core.
Inventors: |
Hoedl; Herbert K. (Concord,
CA), Maury; Eufredo (Concord, CA), Cockle;
Dave (Concord, CA) |
Assignee: |
Royal Eco Products Limited
(Ontario, CA)
|
Family
ID: |
4159879 |
Appl.
No.: |
09/367,046 |
Filed: |
August 6, 1999 |
PCT
Filed: |
February 09, 1998 |
PCT No.: |
PCT/CA98/00073 |
371
Date: |
August 06, 1999 |
102(e)
Date: |
August 06, 1999 |
PCT
Pub. No.: |
WO98/34779 |
PCT
Pub. Date: |
August 13, 1998 |
Foreign Application Priority Data
|
|
|
|
|
Feb 10, 1997 [CA] |
|
|
2197136 |
|
Current U.S.
Class: |
264/254;
264/275 |
Current CPC
Class: |
B29C
43/146 (20130101); B29C 43/18 (20130101); B29C
70/70 (20130101); B29L 2031/7178 (20130101) |
Current International
Class: |
B29C
43/18 (20060101); B29C 43/14 (20060101); B29C
70/00 (20060101); B29C 70/70 (20060101); B28B
007/22 () |
Field of
Search: |
;264/254,255,275,279,328.8 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
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1119503 B29 |
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Dec 1961 |
|
DE |
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43 01 444 A1 B29 |
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Jul 1964 |
|
DE |
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43 22 888 A1 B29 |
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Jan 1965 |
|
DE |
|
1241594 B29 |
|
Jun 1967 |
|
DE |
|
0 578 466 A1 |
|
Jul 1993 |
|
EP |
|
1234237 B29 |
|
Oct 1960 |
|
FR |
|
2287995 |
|
May 1976 |
|
FR |
|
2262469 |
|
Jun 1963 |
|
GB |
|
Other References
Masakazu, Matsufuji (Inventor) Patent Abstracts of Japan, No.
02050810, Feb. 20, 1990. .
Tadashi, Yamamoto (Inventor) Patent Abstracts of Japan, No.
58147331, Sep. 2, 1983..
|
Primary Examiner: Cuomo; Peter M.
Assistant Examiner: Anderson; Jerry A.
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A method of completely encapsulating an insert or core in
plastic material characterized by placing said insert or core in
and supporting it on one side of a mold tool having a core side and
a cavity side whose perimeters are greater than the perimeter of
said insert or core and having means to confine plastic flow within
said mold tool while permitting plastic to flow around and cover
the periphery of said core or insert, introducing a first charge of
plastic between said insert or core and the other side of said mold
tool, distributing said plastic material under pressure with said
plastic in molten state to coat the upper side and periphery of
said insert or core with a plastic layer, separating said mold
sides while said plastic is still hot to utilize the adhesive
properties of said plastic layer to fix said insert or core to said
other mold side to lift said insert or core off said one mold side,
and while said plastic from said first charge is still hot
introducing a second charge of plastic into said one mold side
underneath said insert or core, and distributing said second
plastic charge under pressure with said plastic of said second
charge in a molten state to coat the underside of said insert or
core with a plastic layer and to unite with the hot plastic from
the first charge covering the periphery of said core or insert to
provide on cooling a completely continuous plastic layer completely
encapsulating said insert or core.
2. A method as claimed in claim 1 characterized in that said first
and second plastic charges are introduced into said mold in a
molten state.
3. A method as claimed in claim 2 characterized in that said
plastic material is a thermoplastic material.
4. A method as claimed in claim 2 characterized in that said
plastic material is a thermoset material.
5. A method as claimed in claim 1 characterized in that said mold
tool is a heated tool and said plastic material is heated to a
molten state in said heated tool.
6. A method as claimed in claim 4 characterized in that said mold
tool is a heated tool and said thermoset plastic material is heated
to a molten state in said heated tooling.
7. A method as claimed in claim 1 characterized in that said first
charge of plastic material is introduced between said insert or
core in a molten state and is distributed under pressure by closing
said mold tool.
8. A method as claimed in claim 1 or 7 characterized in that said
second charge of plastic is introduced underneath said insert or
core and is distributed under pressure by closing said mold
tool.
9. A method as claimed in claim 1 characterized in that said core
is a rigid planar member.
10. A method as claimed in claim 1 characterized in that said core
is a member formed of foam material.
11. A method as claimed in claim 10 characterized in that said foam
member has open cells and said plastic material is forced into said
open cells during distribution of said plastic material under
pressure to encapsulate said core.
12. A method as claimed in claim 1 characterized in that said core
has a composite structure comprising a central foamed member
wrapped in a surrounding glass mat, and said plastic material is
forced into the interstices of said glass mat and foam cells during
distribution of said plastic material under pressure to impregnate
said glass mat and enter said foam cells.
13. A method as claimed in claim 1 characterized in that said mold
sides have telescoping edges.
14. A method as claimed in claim 1 in which a second insert or core
is encapsulated beneath said encapsulated insert or core by
repeating the steps recited in encapsulating core while the plastic
material of said plastic charges and are still hot.
Description
FIELD OF THE INVENTION
This invention relates to plastic molding processes and products
produced thereby and more particularly to a plastic molding process
wherein insert members or cores inserted into a mold are completely
encapsulated by the plastic introduced into the mold during the
molding operation.
BACKGROUND OF THE INVENTION
Insert molding is a widely used method to incorporate functional
components such as metal pins, screws, electrical contacts, etc.
into a plastic injection molding. These functional components are
typically inserted at predetermined locations in the open molding
tool which comprises a core side and a cavity side which when
brought together or closed define the desired mold shape. After the
functional components have been inserted, the tool is closed, and
the molten plastic is injection into the cavity. The molten plastic
flows around these inserts and after appropriate cooling the part
can be removed from the tool with these inserts partly incorporated
in the plastic body.
Similar insert molding techniques are used for compression molding
of e.g. polyester based Sheet Molding Compound (SMC). Here the
functional part is inserted in the core and/or cavity side while
the tool, which is heated, is open. Next the SMC is loaded into the
tool and, as the tool is closed, the polyester SMC starts to flow
under heat and pressure, filling the cavity and flowing around the
inserts. After appropriate curing time the part can be removed from
the tool with the inserts partly incorporated in the plastic
body.
Another technique utilizes the insertion of a preformed metal or
plastic skin into the cavity side of the mold and the insertion of
devices by means of which the part to be molded is to be fastened
to other parts into the core side of the mold. The skin and the
fastening devices are then combined with the injection of e.g.
structural foam to produce one integral piece such as automotive
bumper guards.
Other known techniques involve the molding of thermoplastic
material onto or around another component, such as Outsert Molding.
This process uses a technique where an object is placed at the
parting line between the core and cavity of a tool and actually
extends out of the tool. After closing of the tool molten material
is injected into the cavity and the portion of the object which is
inside the cavity is being covered with plastic.
These known methods of insert molding mentioned above involve the
placements of the inserts into the core or cavity side of the mold
prior to molding resulting in only a portion of the insert being
anchored into the plastic moldings.
One example of actual encapsulation of almost 100% of a core into
an injection molding is the so called "Lost Core" molding technique
used to produce complicated hollow plastic components such as
engine intake manifolds. In this method, a metal alloy is first
cast into a shape which resembles the hollow interior of the
plastic components to be produced. This metal component or core is
then placed into an injection molding tool at a predetermined
location and held in place by e.g. pins, moving side cores, or in
certain locations by the tool parting line. The gap between the
metal components and the cavity wall determines the wall section of
the finished plastic part.
Following the securement of the metal component, the tool is then
closed and molten plastic is injected between the metal component
or core and the walls of the cavity. After appropriate cooling the
plastic part with a metal core is removed from the tool and placed
into a hot oil bath. The metal core is melted by the hot oil and
can escape through the openings formed during the injection molding
process where the metal core was held in place in the tool prior to
molding. The resulting plastic part is hollow, similar to a blow
molding, however more complex and with very smooth inner walls.
A technique for encapsulating prefabricated cores with an injected
liquid resin is known under the name of Resin Transfer Molding
(RTM). This technique involves the fabrication of e.g. a foam core
surrounded by several fiberglass mats. This prefabricated core is
placed into a tool. The tool is closed and a liquid resin such as
epoxy resin is injected into the space provided between the fibers
of the fiberglass mat to totally encapsulate the foam core.
Sometimes vacuum is applied to the tool, assisting the flow of the
resin and the complete wet out of the fiberglass mat. After curing
of the epoxy resin, the part can be removed from the tool. This
technique is used, for example to produce lightweight and stiff
automotive hoods.
These known techniques directed at encapsulating a core or insert
involve a mechanical means to keep the core in a predetermined
distance from the cavity walls by means of e.g. pins (Lost Core) or
a fiberglass mat (RTM) which enables the core to be almost
completely encapsulated. It is the object of the present invention
to enable the complete encapsulation of a core or insert without
the use of pins or other locating means.
DE-A-430144 discloses a method of encapsulating a core or blank by
a first molding operation in which the blank is supported on a
first mold part matching its shape and its exposed upper surface
covered by a layer of plastic injected into a second mold part
having a greater perimeter than the blank to provide a projecting
plastic border around the blank perimeter. Then in a subsequent
second molding operation using a third mold part having a perimeter
greater than the blank, the undersurface of the blank is covered by
a layer of plastic which extends beyond the perimeter of the blank
to again provide a plastic border to butt against the plastic
border produced in the fist molding operation. Such a method
requires two molding operations using different tooling to effect
the encapsulation and results in a butt joint around the perimeter
of the blank.
SUMMARY OF THE INVENTION
The present invention resides in providing a molding operation
which enables the total encapsulation of a core or an insert or
inserts in a surrounding plastic material by the utilization of the
plastic material itself to secure the core or insert in position
within the enveloping plastic during the molding operation.
In this respect, the invention utilizes the adhesive properties
which plastic material exhibits while still hot combined with a
multi stage molding operation wherein a core or insert is placed in
one side of a mold. A first charge of plastic material is
introduced between the core or insert and the other side of the
mold and the mold is closed with the plastic material in a molten
state to coat the exposed surfaces of the core or insert with a
plastic layer. The mold is then opened while the plastic layer is
still hot causing the core or insert which is adhered to the other
side of the mold by the hot plastic layer to be removed from the
one mold side. A second charge of plastic material is then
introduced into the mold side from which the core or insert has
been removed. The mold is then closed with the plastic in a molten
state to coat the remainder of the insert or core.
In the preferred form of the invention, the charges of plastic
material are charges of thermoplastic material introduced into the
mold while in a molten state. However, it will be understood that
thermoset plastic material may also be used and that, through the
use of heated tooling, the plastic charges can be heated in the
mold as part of the molding operation.
It will be understood that the quantity of plastic introduced into
the mold in each of the plastic charges will determine the
thickness of the surrounding or encapsulating layer of plastic.
It will also be understood that the molding steps can be repeated
to encapsulate two or more inserts.
The molding process of the invention in which inserts or cores are
totally encapsulated with a continuous plastic film or layer gives
rise to novel totally encapsulated products and structures which
heretofore could not be produced and the invention further relates
to such novel products and structures.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of an open mold in which an insert
or core has been placed on the core side of the mold and a first
charge of plastic, which in the preferred embodiment of the
invention is a viscous molten thermoplastic, has been introduced
into the mold on top of the insert or-core, that is, between the
insert and the cavity side of the mold preparatory to the closing
of the mold.
FIG. 2 shows the mold of FIG. 1 in the closed position showing the
molten plastic charge compressed to flow and cover the upper
surface and the periphery of the insert or core as enabled by the
spacing between the perimeter of the mold and the perimeter of the
insert.
FIG. 3 shows the next step in which the mold is open while the
plastic material is still hot causing the plastic material through
its adhesion to the insert or core and to the cavity side of the
mold to carry the insert or core off the core side of the mold and
showing a second charge of viscous molten plastic introduced into
the mold on the core side of the mold, that is, between the insert
or core and the mold core side.
FIG. 4 shows the further step in which the mold has been closed
again causing the second charge of molten plastic to spread and
cover the underside of the insert or core and to meet the still hot
plastic of the first charge around the perimeter of the insert or
core to complete the encapsulation of the insert or core.
FIG. 5 is a view showing the mold open again and the completely
encapsulated insert or core being removed after the plastic
material has cooled sufficiently to harden.
FIGS. 6 through 12 illustrate the molding steps corresponding to
those shown in FIGS. 1 through 5 for encapsulating two inserts or
cores.
FIG. 6 corresponds to FIG. 1 showing a first insert or core placed
on the core side of the mold and the first charge of viscous molten
plastic material introduced into the open mold on top of the first
insert or core.
FIG. 7 corresponds to FIG. 2 and shows the mold closed.
FIG. 8 is similar to FIG. 3 but in this case a second insert or
core has been placed on the core side of the mold and a second
charge of viscous molten plastic has been placed on top of the
second insert or core.
FIG. 9 shows the mold closed and showing the first insert or core
fully encapsulated and the second insert or core having its top
surface and perimeter covered with the compressed and distributed
plastic charge.
FIG. 10 shows the second opening of the mold this time while the
plastic material is still hot and a third charge of viscous molten
plastic material introduced into the mold between the underside of
the second insert or core member and the core side of the mold by
being deposited on the core side of the mold.
FIG. 11 shows the third closing of the mold to complete the
encapsulation of the second insert or core.
FIG. 12 shows the final opening of the mold after the plastic
material has hardened sufficiently on cooling that the multi insert
or core encapsulated product can be handled and removed.
FIGS. 13 to 17 correspond to FIGS. 1 to 5 inclusive but showing a
different insert or core structure.
FIG. 18 is a broken away vertical section on an enlarged scale of
the encapsulated insert or core produced by the molding operations
of FIGS. 1 to 5 inclusive.
FIG. 19 is a broken away vertical section on a large scale of the
encapsulated dual or multi-core product produced by the molding
steps of FIGS. 6 to 12 inclusive.
FIG. 20 is a broken away vertical sectional view on an enlarged
scale of the encapsulated insert or core produced by the molding
steps of FIGS. 13 to 17 inclusive.
FIG. 21 is a view similar to FIG. 18 but showing the insert or core
as comprising a composite sandwich of material.
FIG. 22 is a broken away perspective view illustrating where the
products produced by FIGS. 1 to 5 inclusive and FIGS. 13 to 17
inclusive are being used to form a pallet with the pallet being in
the process of being assembled.
FIG. 23 is a broken away vertical sectional view of the assembled
pallet of FIG. 22.
DETAILED DESCRIPTION ACCORDING TO THE PREFERRED EMBODIMENTS OF THE
PRESENT INVENTION
Returning first to FIGS. 1 to 5, FIG. 1 shows a molding tool or
mold comprising a core side 1 and a cavity side 2 with the mold in
the open position and an insert 3 which may, for instance, be a
wafer board having a dimension slightly less than the dimension of
the mold sides so that the edges 4 of the insert or core 3 stop
short of the edges 5 of the core side 1.
Placed on top of the insert 3 is a charge 6 of plastic material,
preferably a viscous molten thermoplastic material, having a
predetermined measured quantity so that, when the mold is closed
under pressure to the position shown in FIG. 2, the plastic
material will be spread as a thin layer 7 covering the upper
surface 8 and edges 4 of the insert or core with the plastic
material being confined at the edges 4 of the insert by the
perimeter walls or edges 9 of the cavity side 2 of the mold which
telescopically engage the core side edges 5 as shown in FIG. 2.
Following closure of the mold under pressure to spread the plastic
material 6 to cover the upper surface and edges of the insert or
core 3, the mold is then opened as illustrated in FIG. 3 while the
plastic material is still hot utilizing its viscosity or adhesive
qualities to secure the material to the cavity side of the mold and
to the core or insert 3 to remove the insert from the core side of
the mold. Thus, the layer 7 of plastic material now forms the means
of supporting the insert or core in the mold without requiring any
pins or other support mechanism and the thickness of the plastic
layer 7 determines the spacing between the cavity side of the mold
and the core, that is, the location of the core.
Also as shown in FIG. 3 a second charge 6' of viscous molten
plastic material as aforesaid is introduced into the mold by
placing same on the core side 1 of the mold following which the
mold is closed as illustrated in FIG. 4 wherein the second charge
6' of the molten material is spread as a thin layer 7' to cover the
undersurface 10 to complete the encapsulation of the core by
uniting with the still hot plastic material of the layer 7 at the
boundary or edges 4 of the core 3.
Following cooling and hardening of the plastic layers 7 and 7', the
mold is opened as illustrated in FIG. 5 and the encapsulated core
removed.
FIGS. 1 to 5 illustrate a molding operation carried out with the
molding tool arranged conveniently in a horizontal position with
the core side 1 oriented beneath the cavity side 2. It will be
understood that the arrangement could be reversed with the cavity
side 2 disposed beneath the core side 1 in which case the insert or
core 3 would first be placed in the cavity side 2 of the mold and
the first charge 6 of molten plastic material introduced into the
cavity side of the mold on top of the core 3 and, in the sequence
of molding steps, the roles of the cavity and core sides of the
molds would be reversed throughout the sequence of mold steps to
obtain the completely encapsulated insert or core 3.
As illustrated in FIGS. 1 to 5, the core side 1 of the mold is
formed with a pair of circular channels 11 having tapered center
posts 12 into which material from the charge 6' is forced under
pressure to provide the dependent annular hollow rings 13 on the
underside of the encapsulated core as illustrated in FIG. 22.
It will be understood that the core side and as well the cavity
side of the mold may be formed to provide ribs, grooves or designs
as desired in the encapsulating plastic layers 7 and 7'.
FIGS. 6 to 12 illustrate the application of the method to provide a
product having a multiple layers of inserts or cores which are
completely encapsulated.
As in the case of FIGS. 1 to 5, the method is illustrated with the
mold tool in a horizontal position with the core side 1 below the
cavity side 2.
With this arrangement of the tooling, a first insert or core 14 is
placed on the core side 1 of the mold and a first charge 15 of
viscous molten thermoplastic material is placed on top of the core
14 as illustrated in FIG. 6. Then, as illustrated in FIG. 7, the
mold is closed under pressure to spread the plastic material to
cover the upper surface 16 and the edges 17 of the core 14.
Again, as illustrated in FIG. 8, the mold is open and the layer 18
of the plastic material adhering to the cavity side 2 of the mold
and the first core 14 carries the first core 14 up away from the
core side 1 of the mold at which time a second insert or core 19,
shown in FIG. 8 as having the same dimensions as the first core 14,
is placed on the core side 1 of the mold and a second charge 20 of
viscous molten thermoplastic material as aforesaid is placed on top
of the second insert 19.
The mold then is closed under pressure as illustrated in FIG. 9 and
a second charge of plastic material 20 is spread to complete the
encapsulation of the first core 14 and to cover the upper surface
21 and the edges 22 of the second core 19 with plastic layer
18(a).
Again, while the plastic material of both the first charge 15 and
the second charge 20 are still hot, the mold is opened as shown in
FIG. 10 with the adhesive bond of the plastic with the cavity mold
side 2 and the cores 14 and 19, the fully encapsulated core 14 and
the partially encapsulated core 19, are removed from the core side
1 of the mold. A third charge 23 of viscous molten thermoplastic
material as aforesaid is then placed on the core side 1 of the
mold. The mold is again closed under pressure to complete the
encapsulation of the second core 19 with a plastic layer 18(b) as
illustration in FIG. 11. Upon cooling, the mold is opened and the
multiple core product 24 removed from the mold.
FIGS. 13 to 17 illustrate the molding method being carried out to
produce a pair of members having totally encapsulated cores which
in the example given are to form the bottom members or runners of
the pallet illustrated in FIG. 22.
In this case, a pair of inserts or core members 27 are placed in
the correspondingly shaped dual wells 28 in the core side 29 of a
molding tool arranged below the cavity side 30.
Next a charge of viscous molten thermoplastic material 31 is placed
on the core side 29 of the mold on top of the core members 27 and
the mold closed under pressure to provide a layer 32 of plastic
covering the exposed surfaces of the core members 27, the thickness
of the layer being dependent upon the quantity of plastic material
in the charge 31.
Again, while the plastic material 31 is still hot, the mold is
opened as illustrated in FIG. 15 with the plastic material adhered
to the cavity side of the mold and to the core members 27 to carry
them away from the core side 29 of the mold.
A second charge 31' of viscous thermoplastic material as aforesaid
is introduced centrally into the core side 29 of the mold and the
mold is again closed under pressure as illustrated in FIG. 16
causing the second charge of plastic 31' to spread and complete the
encapsulation of the core members 27 with a horizontal layer 33
extending across the bottom of the core members 27 and inclined
layers 34 joining the bottom layer 33 with the layer 32.
Again, the core side 29 of the mold is shown as having circular
channels or grooves 35 with tapered center parts 36 to produce
hollow mounting rings 37.
After removal from the mold, the encapsulated core members 27,
which comprise pallet runners 38, are separated and incorporated
into a pallet designated at 39 ( FIGS. 22 and 23) comprising the
upper platform 40, runners 38 (only one being shown) connected by
spacers 41 which are welded, preferably by spin welding, into the
annular rings or channels 13 and 37 of the pallet platform 40 and
the pallet runner 38 as illustrated in FIG. 23.
FIG. 18 is a cross-section of a corner portion of the product
produced by the process of FIGS. 1 to 5 showing the core or insert
3 encapsulated by the layers 7 and 7' from the material of the
plastic charges 6 and 6' respectively.
While the core 3 may, for instance, be wafer board, it may be any
other desired insert such as a foamed product or a composite
product such as illustrated in FIG. 21 which comprises a central
foam layer 42 wrapped in a fiber glass mat 43 with the plastic
layers 7 and 7' wetting the glass mat and penetrating open pores of
the foamed central portion 42 of the composite insert.
It will be understood that the plastic charges 6 and 6' may have
different compositions or colours as desired so that the layers 7
and 7' can be coloured differently, have different compositions and
different characteristics.
FIG. 19 illustrates a cross-section of a corner of the product
produced by the process illustrated in FIGS. 6 to 12 where a pair
of inserts 14 and 19 are encapsulated in plastic. Again, it will be
appreciated that these inserts may be the same or different as
discussed in connection with FIG. 21.
Additionally, the method of encapsulating two inserts as
illustrated in FIGS. 6 to 12 can be continued to encapsulate three
or more separate inserts or cores to incorporate for instance a
central insert of foamed material sandwiched between two separate
wafer board inserts.
FIG. 20 is a cross-section of one of the corners of one of the
encapsulated inserts 27. Again the insert or core 27 may take
different forms including a composite core such as discussed with
respect to FIG. 21.
While the preferred method for the method of the present invention
is the use of a compression molding process using horizontally
mounted tools with telescoping edges with either the core or cavity
side facing upwards for easy placement of the core or cores, the
method can be carried out using the injection or
injection/compression molding process with either horizontally or
vertically mounted tooling as long as telescoping edge tooling or
other means such as moving side cores to contain the liquid plastic
material is used. In this latter case, a system for securing the
position of the core or prefabricated core materials must be
provided during the first injection step, that is, until the
process has proceeded until the hot plastic through it adhesive
properties fixes the insert in position in the mold.
When using the injection or injection/compression molding process
with vertically mounted tooling in addition to the provision for
the containment of the liquid material and for initially securing
the position of the core or prefabricated cores in position until
they are secured by the adhesive property of the plastic material,
one or more apertures in the prefabricated core may be necessary to
inject the first charge of molten material through the core into
the core or cavity side of the tool.
As mentioned, the preferred type of materials in carrying out the
method of the invention are thermoplastic materials which can be
used with water cooled tools. However, thermoset materials such as
polyester S.M.C., epoxy and the like can also be used and rather
than introducing the charges of plastic material into the mold in a
molten state they may be brought to the molten state by heated
molds or tools as part of the molding operation.
Although various preferred embodiments of the present invention
have been described herein in detail, it will be appreciated by
those skilled in the art, that variations may be made thereto
without departing from the scope of the appended claims.
* * * * *